Magnetic tape is commonly used for storage of digital data. The magnetic tape is spooled on reels in a cartridge that is insertable into a digital data transfer apparatus in which data can be written onto the tape and/or data can be read from the tape. Such data transfer apparatus, which may be referred to as a tape drives, typically includes a tape head for one or both of reading and/or writing data from or to the tape head.
Known tape drives are generally designed to use a predetermined size tape cartridge that contains tape having a known width. Known cartridge loading devices of tape drives are generally designed to be used with a particular size of cartridge. Such devices conventionally include means for ensuring that only cartridges of the correct size can be inserted and then only when the cartridge is correctly oriented. A feature of known cartridge loading devices is that they are made rigid so that cartridges of the wrong size or incorrectly oriented cartridges cannot be forced into the tape drive, except by the exertion of an unnatural amount of force.
One format for data storage in a helical scan tape drive is Digital Data Storage (DDS). Various versions of DDS exist, but each version uses the same width tape in Digital Audio (DAT) cartridges, including DAT72 and DAT160. The tape width is approximately 4 mm. There is a demand for more and more data storage capacity. This has, to some extent, been met by improved reading and writing techniques that have allowed increased amounts of data to be stored, without changing the tape length or width. However, ultimately, the storage capacity of a given size of tape has a limit.
One solution to the problem of data storage capacity is to increase the width of the tape. Of course, a greater width provides more storage capacity. However, since the cartridge loading devices of tape drives are designed to accept a particular size cartridge, if wider tapes are used, tape drives with loading devices able to accept a larger cartridge must be provided. This then provides the user with the problem that legacy format tape cartridges would not be usable with the new tape drive and so it would be necessary to maintain more than one tape drive or transfer existing stored data to the wider tape.
Conventional cartridge loading devices that can only accept a single size of cartridge are designed in such a way that cartridges can only be inserted when correctly oriented. To this end, conventional cartridge loading devices are of rigid construction and equipped with means, such as ramps or ribs, that interact with formations on the cartridge to prevent insertion in any but the correct orientation. The result is that an incorrectly oriented cartridge can only be inserted by using an unnaturally large force, usually such as would result in damage to the device and/or cartridge.
The applicant is proposing a new cartridge loading device that can expand in such a way that it can accept different sized cartridges. By this means, a single device can be used with tapes having different widths. In such a cartridge loading device, it remains desirable to have means for preventing the insertion of incorrectly oriented cartridges. However, the conventional means rely on the rigidity of the cartridge loading device.
FIG. 1 shows the underside of a conventional DAT cartridge 1. The cartridge 1 is generally rectangular and comprises a two-piece body 2, a slider 3 mounted on the lower half of the body and a lid 4 hinged to the front side of the upper half of the body. The slider 3 has two grooves 5 formed in its side that faces away from the body 2. Each groove has two apertures 6, 7 formed in its base. There the apertures 6 are at the front end of the respective grooves and the apertures 7 are at the rear end. The lower half of the body 2 is provided with two detents 8, one for each groove 5. In the position of the slider 3 illustrated in FIG. 1, the detents 8 are engaged in the rear end apertures 7. The cartridge contains a supply hub and a take up hub (not shown) around which the tape is spooled and the lower half of the body 2 has respective spindle apertures (not shown) to permit spindles of a spindle drive to engage the hubs. The slider 3 also defines two apertures 9 and can be slid to a position in which the apertures overlie the spindle apertures to permit access to the hubs.
In order to access the tape contained within the cartridge, it is necessary for the slider 3 to be slid away from the front side of the cartridge 1 toward the rear. This brings the apertures 9 into line with the spindle apertures so that the spindle drive can be raised to engage with the hubs. Rearward movement of the slider 3 also provides access to the lid 4 which is pivotted clockwise (as viewed in the drawing) to allow the tape to be drawn forward from the cartridge to bring it into contact with the tape head.
In order to cause the slider 3 to slide to the rear of cartridge body 2, tape drives are conventionally provided with small ribs (for example, see the ribs 57 on the floor 56 of the cartridge loading device 10 shown in FIG. 2). As the cartridge is slid into the cartridge loading device, the ribs 57 enter the respective grooves 5 at their front ends. As the cartridge 1 is inserted further into the cartridge loading device, the grooves 5 slide over the ribs 57 until the ribs engage and press the detents 8 down and out of the rear end apertures 7. This releases the slider 3 and continued insertion of the cartridge results in the slider being pushed rearwardly on the body 2. When the cartridge is fully inserted, the ribs are clear of the front end of the grooves allowing the detents 8 to penetrate the front end apertures 6 and so lock the slider in place. Once the slider is pushed back, the lid can be raised and the tape drawn forwardly from the cartridge by a tape guide assembly (not shown). When the cartridge is withdrawn from the cartridge loading device, the ribs 57 push the detents 8 out of the front end apertures 6 allowing the slider 3 to be slid toward the front side of the cartridge by a spring until the detents 8 engage in the rear end apertures 7.
It is important that the ribs 57 should properly engage in the grooves 5 and move the slider 3 to its rearward position. Without this, the lid 4 cannot open and the spindle drive will punch a hole through the underside of the cartridge, rather than passing through the apertures 9 and into engagement with the hubs.
The grooves 5 and ribs 57 are relatively small features. The grooves have a standard width of around 3 mm and a depth of 0.65 mm±0.05 mm. Therefore, in order for the ribs 57 to function, the tolerances in production of the cartridge loading device 10 and the cartridge must be kept tight. For example, if the height of the opening in the cartridge loading device 10 into which the cartridge is inserted is just a little too large, the cartridge could simply “float” over the ribs 57, which would then not penetrate sufficiently deeply to release the detents and slide the slider to the rear of the cartridge.
In conventional cartridge loading devices having a one size opening, the construction is rigid and it is possible to manufacture to tolerances that should ensure the ribs 57 function every time a cartridge is inserted into the cartridge loading device. In an expandable cartridge loading device as proposed by the applicant, this is more problematical, since there will be parts that move relative to each other in order to provide the expansion and this makes it more difficult to manufacture to tight tolerances.
Yet another problem is that the apparatus in which the cartridge loading device is housed must have an inlet aperture that is sufficiently large to allow the insertion of the different sizes of cartridge to be used. The inlet apertures of conventional apparatus can be sized to control the orientation of the cartridge when it is inserted into the cartridge loading device. That is, the inlet aperture can be sufficiently close to the size of the cartridges it is designed to receive as to ensure that when cartridges are inserted into the cartridge loading device, they are not inclined or twisted with respect to the XYZ axes of the device. This is not possible with an inlet aperture that must allow the insertion of two sizes of cartridge. The inlet aperture can be used to provide control of the orientation of the larger of the two sizes of cartridge in the conventional way. However, it cannot control the orientation of the smaller size of cartridge. Thus, as illustrated by the arrow 200 in FIGS. 7, 9 and 10, the smaller size of cartridge can be inserted into the cartridge loading device while inclined downwardly with respect to the cartridge loading device. This makes it possible for the smaller size cartridge to be inserted into the cartridge loading device in such a way that the grooves 5 ride over the ribs 57 and so the detents 8 are not released and the slider 3 does not slide back.